That's largely a matter of opinion, and you must factor in what counts as a detriment or benefit, which varies with 4chan's goals. Arguably 4chan doesn't really have a goal, though some (particularly the alt-right type people) would say it's a detriment, and people like me or some users of non-political boards think it's a benefit, as one of the large concerns is that /pol/ is infecting other boards, despite the fact that it was made as a containment board.

Others boards such as /mlp/ however do not show such growth into other boards, perhaps because the rule against ponies is stronger than the rule against racism.

"Containment" boards are pure fantasy, they just give the worst users a place to coordinate their attacks on other boards.